Deep, narrow-band Ha and 6584 AA [Nii ] CCD images of the peculiar, infrared excess B[e] star MWC~922 reveal a collimated, bipolar jet orthogonal to the previously detected extended nebula. The jet consists of a pair of $sim$0.15 pc segments on either side of MWC~922 separated by gaps. The most distant jet segments disappear $sim$0.6 pc from the star. The northwest beam points to a faint emission-line feature 1.65 pc from MWC~922 that may be a terminal bow shock where the jet rams the ambient medium. The narrow opening-angle of the jet combined with an estimated internal sound speed of $sim$10 kms implies a jet speed $sim$500 kms . The previously detected nebula extends up to 0.6~pc to the southwest of MWC~922 at right angles to the jet and appears to be an extension of the compact, edge-on disk surrounding the star. It points toward the HII region Messier 16 located $sim$1degr ($sim$30 pc in projection) to the southwest. This nebula and jet appear to be externally ionized by the ambient Lyman continuum radiation field and have electron densities of n$_e sim$ 50 to 100 cm$^{-3}$. The southwest nebula and jet have similar surface brightness in Ha and [Nii ]. Faint 70 $mu$m emission traces the southwest ejecta that likely originates from $sim$50 K dust embedded in the photo-ionized plasma which may shadow the dimmer ejecta northeast of MWC~922. MWC~922 may be a massive member of the Serpens OB1 or OB2 associations surrounding Messier 16 and Sh2-54.
Download